It is proposed to continue our studies of the formation of gallium(III) has been relatively neglected when compared to other trivalent metals such as aluminum(III) and iron(III). Determination of gallium(III) chelate formation is complicated by the strong tendency of gallium(III) to hydrolyze complexes at high pH. These strong hydrolytic side reactions compete with chelating agents and must be considered in calculating the stability constants of the metal chelates that form in solution. The reactions of gallium with various chelating ligands will be measured by potentiometric, spectrophotometric, and polarographic techniques. On the basis of the limited information in the literature and of the work recently completed on this project, it is planned to investigate chelating ligands having donor groups that have high affinity for the gallium(III) ion. Examples of such donor groups are: phenolate, phosphonate, carboxylate, and hydroxamate. Some of the most promising ligands having various combinations of these donor groups are not available commercially and will have to be synthesized. It is expected that the results of this research program will make available for experimental cancer studies a variety of gallium(III) chelates with a wide range of stability. Many of these chelates will be sufficiently stable to maintain their integrity in competition with the natural chelating agents present in physiological systems.